Fuse device



Nov. 17, 1931. A. J. ESSER 1,832,194

' FUSE DEVICE Filed March 27,1929 2 Sheets-Sheet 2 I N VEN TOR.

ARTHUR d. 5555K.

A TTORNEYS readily available,

Patented Nov. 17, 1931 ARTHUR J. ESSER, OF DETROIT, MICHIGAN FU' SE DEVICE Application filed March 27, 1929. Serial No. 350,159.

This invention relates to fuses and particularly fuses of a well known type comprising a plug carrying a fusible element and adapted to be screwed into a suitable socket.

It is a common practice among users of electric current upon burning out of such a fuse, to tamper with the fuse socket if no plug of the proper type and ampere capacity is so as to form a short circuit across the socket terminals, or else to insert a fuse plug having an excessive ampere capacity. One quite common expedient is the clamping of a coin in the fuse socket by means of a burnt-out fuse plug, so as to short circuit the socket by such coin. Such practices are dangerous and a not infrequent cause of fires and resultant property losses.

An object of the present invention is to safeguard a plug and socket type of fuse against short circuiting by a coin or slug and to render difficult a short circuiting in any other manner.

Another object is to provide meanswhereby after a building has been completely wired and provided with a plurality of circuits each including a conventional form of fuse socket,

upon determination of the safe load each of said circuits is adapted to carry, each of the sockets may be guarded against the reception of fuse plugs designed to carry a greater load than the desired maximum safe load for the particular circuit in which the socket is connected.

Another object is to differentiate fuse plugs of different standard amperages by the form of their central terminals and to provide members of an insulating nature selectively insertable in a conventional form of fuse socket and formed with openings so corresponding to said plug terminals as to prevent the operative insertion in such socket of any plug of excessive ampere capacity.

These and various other objects the invention attains by the construction hereinafter described and illustrated in the accompanying drawings, wherein: Fig. l is a view in axial sectional elevation of an ordinary plug and sccket fuse, modified in accordance with this invention.

Fig. 2 is a view of the socket member of plugs with respect tral terminals.

such a fuse in side elevation and partial axial section, indicating the manner of inserting an insulating disc therein.

Fig. 3 is a view in elevation of a series of fuse plugs differing as to their ampere rating,

showing one method of differentiating sai to the form of their censerted in an ordinary fuse socket to exclude use of all but one of ure 5.

Fig. 7 is a more or less diagrammatic plan view of a multiple socket base from which a plurality of separate circuits are adapted to branch out from the main supply circuit showing the adaptation of the present invention thereto, and one plug for each circuit beingremoved to show the size of the opening in the insulating safety plug cooperating therewith.

In these views, the reference character 1 designates the ordinary insulating base of a fuse socket member, having the usual integrally projecting collar 2 within which a screw thread. forming sleeve 3 is permanently secured in any suitable. manner and is connected by a conductor 4 to one of the ter-' minal forming screws 5. The socket member further v comprises a central contact formed by a screw 6, headed within the bottom portion of the sleeve 3, and extending through the base 1 for engagement by a conducting strip '2 leading to the other termi nal screw the plugs shown in Fig- 11 has one of its ends connected members for selective '60 3, but

in any suitable manner to a screw-threadforming sleeve 12 permanently embracing the body 9, and its other end connected to a plug-like contact .18, peculiar to the presannular shoulder 15, sa1d disc having a central opening '16 just large enough to receive correspondingly the plug terminal 13 which is just long enough'to pass through the disc and bear against the contact 6. Preferably the disc is marginally beveled to adapt it to fit snugly enough into the circumferential channels formed by the threads of the sleeve 3 to prevent its ready removal. In inserting said disc, it may spring the sleeve 3 slightly to permit it to pass the spiral corrugations of the sleeve 3, the corrugations yielding to permit the disc to be forced permanently into its position of use.

As so far described, the invention safeuards a fuse of plug and socket type against ready short circuiting by coins or other conductors inserted in the socket member of the fuse,'inasmuch as the disc 14 will hold such coins or other conductors out of contact with the contact 6. By a further development of the invention there may be prevented the operative engagement with a fuse socket of a fuse plug having an excessive ampere capacity. 'Thus, fuse plugs difiering as to their ampere capacity may also be differentiated as to some certain dimension of the central terminal 13 of said plugs, and the central openings of the disc-shaped inserts 14: to be used with said plugs may be varied in size. Thus, as shown in Figure 3, the plugs 9a to 9d are identical except as to their capacities and except as to their receptive terminals 13a, 136, 130, and 18d which successively increase in diameter while their lengths are successively and uniformly decreased, and discs 14a to 1461 shown in Figure 4: are varied similarly to said terminals as to the diameters of their central openings 16a, 16?), 160, and 16d, and also as to their thicknesses to cor respond to the varying lengths of the terminals 130;, 13?), 13c and 18d. Thus, it is evident that a fuse socket protected by one of the discs 14 of Figure 3 will not operatively receive plugs of excess capacity, since the central terminals of such plugs can not enter the central opening of said disc. Furthermore, the construction prevents ready adaptation of any of the plugs shown in Figure 3, through filing of its central terminal, to be ,IIISGIiK-ld in a socket intended for a lesser the terminal so filed will still lack the requisite length to project through such disc.

The arrangement shown in Figures 5 and 6 secures the same result in a somewhat different manner by increasing the lengths of the central terminals 13y, 137a, 13Z and 13m according as the capacity. of said plugs is increased, and also uniformly increasing the diameters of said terminals. Correspondingly, the openings 16j,167c, 161 and 16m of the discs 14y to 14m are successively increased in diameter and the thicknesses of said discs successively increased.

In employing the described system of safeguarding fuses, upon original connection of an installation to the supply mains such discs 14: will be inserted in the fuse sockets as will predetermine the maximum capacity plugs to be used in said sockets. When any of the fuses burn out, the customer Will thus be prevented from insertin g excess diameter plugs or from short circuiting the sockets by coins, or the like, as is now commonly done. In other words, it will be impossible to insert a fuse or other member in the socket which will permit an overload to be carried by the particular Wiring system which the fuse is meant to protect.

Fig. 7 is shown to indicate the practical employment of the present invention in con-. nection with the wiring system of a building, such as a home, or the like. In such buildin'gs it is customary to bring the main supply of electric current into the same through a pair of main supply leads, such as 20 and 21, to a single point where the current from the leads 20 and 21 may be split up into a plurality of independent circuits, each sufficing to supply current jects in the building, or the lighting of other current consuming devices in a particular part of the building.

The usual method of accomplishing this is to providea unitary multiple socket base such as 22 in Fig. 7 which is provided with a pluralityof sockets such as'indicated by the numeral 2 in Figs. 1 and 2, and which are indicated in Fig. 7 as 2a to 2h inclusive, size of the base and the number of socketsvarying, particular building to be supplied with current, the number shown being merely for the purpose of illustration.

In the conventional form of these distributor socket bases, as indicated in Fig; 7, the sockets are alternately connected to the opposite leads 20-21, as by the connectors 23, and each socket is provided with a binding post or connector for connecting its opposite side to one side of a circuit. Inother Words,

in the construction shown in Fig. 7 the sockets 2a, 20, 2e and 2.72, are connected to the lead 20, while the remaining'sockets are connected to the lead '21. The opposite sides of the to particular obthe of course, to suit the needs of the sockets 2a to 2b, inclusive, are provided with corresponding connectors 24a to 24k inclusive. The leads 25a and 256 are then employed for one circuit, the leads 25c and 2505 for another circuit, and the leads 25c and 2f and 25g and 25h respectively for another pair of circuits. In practice, these socket bases are installed and the various circuits are laid out and connected with it. The sockets provided on these socket bases must, for practical reasons, be identical at least as far as the relatively permanent portions of the same are concerned, so that up to the time of the present invention at least, it has been impossible with such a type of base to prevent the insertion of a fuse plug of excessive capacity in any one of the sockets connected in a circuit wired for a relatively low capacity.

In the practice of the present invention, when a distributor base such as indicated is installed, and the various circuits are laid out, the safe load for each circuit is then determined and, where the form of constructions shown in Figs. 5 and 6 are employed, a plug 14 corresponding to the maximum desired safe load for any one circuit is inserted in the sockets for that circuit so as to thereafter prevent overloading of the circuit. As an illustration, let it be considered that after the base in Fig.7 has been installed and the various circuits laid out, it is determined that the circuit 25a-25b should not bepermitted to carry over a five ampere load, the circuit 25c-25d a ten ampere load, the circuit 25e25f a fifteen ampere load, and the circuit 25g25h a twenty ampere load. A disc 147' is therefore inserted in each of the sockets 2a and 2b,v a disc 14k in each of the sockets 2c and 2d, a disc 141 in each of the sockets 2e and 2;, and a disc 14m in each of the sockets 2g and 2h. Thereafter the sockets 2a and 21) will be limited to operatively receiving a five ampere fuse plug 97', the

1 sockets 2c and 201 to receiving a 9k fuse plug of five amperes capacity, the sockets 2e and 2; to receiving fifteen ampere fuse plugs 9Z, and the sockets 2g and 2h to receiving a twenty ampere fuse plug 9m. Accordingly, each circuit, after installation, is effectively limited as to future carrying capacity by the simple expedient of inserting one of the plugs 14 of proper size. These plugs 14,

' after being sprung into place, effectively resist removal and are not easily tampered with.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit or substance of the broad invention, the scope of which is commensurate with the appended claims.

What I claim is:

1. The combination with a wiring circuit,

of means for preventing overloading thereof comprising a fuse plug socket operatively connected in said circuit, said socket being capable of receiving fuse plugs of varying capacities, and means for limiting the operativeness of such plugs to those of an exactly predetermined capacity, said means comprising an insulating protector for a contact surface of said socket, said protector formed to prevent operative engagement of a plug of any other capacity with said socket than that predetermined thereby.

2. In combination with a plurality of electrical circuits each adapted to carry a difierent load, each of said circuits having connected therein a fuse plug socket, all of said sockets being formed to receive the same size of fuse plug, fuse plugs receivable in said sockets, each of said plugs having a terminal projection varying directly in length and directly in diameter as the capacity of said plugs, and the socket for each of said cirvcuits being provided with an insulating member cooperating with a contact surface thereof and. cooperable with said terminal projections for limiting the operativeness of the plugs received therein to those having the exact corresponding capacity.

3. In combination with a plurality of electrical circuits, each adapted to carry a different load, each of said circuits having con- .-,nected therein a. fuse plug socket, all of said sockets being formed to receive the same size of fuse plugs, fuse plugs receivable in said a sockets, each of said plugs having a terminal pro ection varying directly in length and in diameter as the capacity of said plugs, and

the sockets for each of said circuits being,

provided with an insulating member cooperating with a contact surface thereof and cooperable with said terminal projections for limiting the operativeness of the plugs received therein to only those having a predetermined capacity.

4. In combination, a socket base provided with a plurality of identical sockets thereon, a. plurality of electrical-circuits each side of which is connected through one of said sockets, at least two of said circuits being adapted to carry different loads, insulator plugs inserted in said sockets and fuse plugs inserted in said sockets after said plugs, said fuse plugs having terminal projecting contact portions varying directly in length and directly in diameter as their capacity and said insulator plugs having openings therein for the passage of said portions therethrough, the depth and the diameter of said openings corresponding with the length and diameter of the projecting contact portions of the fuseplugs of exact capacity to which said circuit is limited.

5. The method of protecting electrical circuits each having connected therein a fuse plug socket against overloading, comprising in providing a series of fuse plugs for said sockets having terminal contact projections varying in length and in diameter directly as their capacity,.providing a series of insulator plugs insertible into said sockets and having central openings therethrough corresponding in size to the Various lengths and diameters of said terminal projections and inserting into each one of said sockets one of said insulator plugs whose said opening will limit the operative reception of said socket to only one size of said fuse plugs, of an exactly predetermined capacity, and will not allow the operative reception of a fuse plug of greater or lesser capacity.

6. In combination with a fuse socket provided with a thin sheet metal sleeve formed with a screw thread, and a central terminal at the bottom of said sleeve, of an insulatg disc retained in the bottom portion of said sleeve and having a central opening registering with said central terminal, said disc having an edge face of less thickness than the pitch of said thread and being of adiameter slightly larger than the minimum diameter of the threaded portion of said sleeve, whereby the permissible deformation of. said sleeve will permit said disc to be forced into position and will maintain it against inadvertent removal therefrom.

, ARTHUR J. ESSEB. 

